In comments likely to leave Gove open to renewed political attack, Dominic Cummings described Cameron as "bumbling" and claimed education reforms were being held back by the lack of support and sense of purpose on the part of the prime minister.
Just days after Gove was ordered to issue an humiliating apology following a row with the home secretary, Theresa May, over policy on combating extremism in schools, Cummings said in an interview with the Times: "As Bismarck said about Napoleon III, Cameron is a sphinx without a riddle.
"Everyone is trying to find out the secret of David Cameron but he is exactly what he appears to be. There's no mystery to him. He had a picture of Macmillan on his wall – that's all you need to know."
Cummings, who has been described as the brains behind Gove's schools "revolution", left his post at the end of January although he has continued to visit the Department for Education to offer advice.
Since departing from his official post, Cummings has been vocal in his criticism of the deputy prime minister, Nick Clegg, amid differences within the coalition over education policy, accusing the Liberal Democrats of "stupid gimmicks".
Clegg has described Cummings as "a rather peculiar former Conservative adviser" who has allowed his former role to go to his head.
However, the comments by Cummings in the Times mark a turning of his fire on Gove's own boss, as well as on others close to Cameron.
He was scathing about the prime minister's chief-of-staff, Ed Llewellyn, describing him as a "classic third-rate suck-up-kick-down sycophant presiding over a shambolic court".
Cummings added: "To get anything done you have to have priorities and there are no priorities. Everyone is discouraged from telling the truth to important people. There's no grip. No focus."
A furious Cameron cracked the whip on the education and home secretaries earlier this month after the two stunned Westminster by abandoning any pretence of cabinet responsibility. The pair had gone public on the eve of the Queen's speech to voice bitter disagreements over who was to blame for failings on one of the most sensitive issues of government policy – the issue of combating extremism in schools.
Following an unusually swift inquiry by the cabinet secretary, Sir Jeremy Heywood, Downing Street issued a statement saying that Gove had written to the prime minister and to Charles Farr – the Home Office's security chief whom he had criticised – to apologise for his behaviour.
The row between Gove and May burst into the open after a briefing Gove gave to journalists at the Times was splashed over the paper's front page.
Gove had told the newspaper over a lunch that he believed the Home Office's failure to combat extremism had allowed a small number of radicals to infiltrate schools in Birmingham, and made clear he blamed May and Farr.
Cummings has maintained a vocal presence on Twitter, using it to lambast opponent's of Gove's aims of undertaking a "cultural revolution" in education.
A day after tweeting that it was "Good to see some hacks realising we're governed by clowns", he tweeted on Friday: "DC thinks the PM job is babbling like an uber-pundit. No priorities/focus/grip. Shambles = normal not aberration. Nxt week 'values' shambles."
Long seen as a driving force in the education department, Cummings worked for Iain Duncan Smith when he was leader of the opposition. After the 2010 election, his appointment as a government adviser was blocked by Andy Coulson, director of communications, on the basis that he might be too independent and too a disruptive force. However, Gove continued to rely on him from a distance and, when Coulson resigned, he appointed him.
guardian.co.uk © Guardian News and Media Limited 2010